1. Field of the Invention
The present invention generally relates to a display panel Comprised of a white color organic luminescent element and a color filter, and More particularly, to an encapsulated organic luminescent display panel Capable of blocking external moisture or oxygen and method for fabricating the same.
2. Discussion of Related Art
In general, a low molecular organic luminescent element or high molecular organic luminescent element (hereinafter, it will be referred to as organic luminescent element) is comprised of an anode formed on a substrate, a hole transport layer for injecting holes to the organic luminescent layer, an organic luminescent layer formed on the hole transport layer, an electron injecting layer formed on the organic luminescent layer and for injecting electrons to the organic luminescent layer, and a cathode connected to the electron injecting layer, and when electrons and holes are injected into the organic luminescent layer through the electron injecting layer and the hole transport layer, the electrons and holes are combined in pairs in the organic luminescent layer to thereby emit light. That is, the light is emitted by energy irradiated during combination of the electrons and holes.
However, the above-mentioned organic luminescent element is apt to be deteriorated by internal or external factors, especially moisture or oxygen permeated from outside adversely affects luminous lifetime of the element. To cope with such problem, several attempts and technologies have been conducted and developed to ensure reliability and stability of the organic luminescent element.
One method for ensuring the reliability and stability of the organic luminescent element is an encapsulation method. The encapsulation method, which is most widely used in the art, includes employing a glass cap or a metal cap. After the metal cap or glass cap is cleaned and dried, a moisture absorbent (e.g., calcium oxide or barium oxide) is applied on the inside of the cap. Ultraviolet (UV) curing type adhesive in an inactive gas atmosphere is employed to allow the cap to be fixed to the substrate (typically, glass) where the organic luminescent element is formed. However, such encapsulation method uses the glass cap or metal cap, so that it is difficult to accomplish a light weight and a thin thickness and many processing time is required. In addition, a large area of the display panel may not be properly encapsulated due to the weight of the cap, and the organic luminescent element with its cap may not be bent.
To help overcome the encapsulation method using the metal cap or glass cap, an encapsulation method using a plastic cap (such as Korean Patent Publication No. 1999-88334), encapsulation methods using physical vacuum deposition or chemical vacuum deposition (such as Korean Patent Publication Nos. 1999-31394, and 1999-38057, U.S. Pat. Nos. 5,188,901, 6,268,695, 6,224,948, 6,207,239, 6,228,436, 5,902,641, 6,217,947, 6,203,854, 5,547,508, and 5,395,644), and so forth have been proposed. However, these conventional methods should still use high-priced equipments (physical/chemical vacuum chamber, vacuum pump, etc.), and they may not be readily applied to an organic luminescent element having a large area.
In addition to the above-mentioned methods, encapsulation methods for spin coating or molding siloxane based high molecule on an organic luminescent element (such as U.S. Pat. No. 5,855,994 to Hans Biebuyck, et al, U.S. Pat. No. 5,734,225, Korean Patent Publication Nos. 1999-44520, 2000-23573), encapsulation methods for applying photo reactive acrylate monomer or initiator on an organic luminescent element by means of spin coating and then forming a cured thin film through light irradiation thereon (such as Korean Patent Nos. 2002-45479, 2002-20908, 2002-75406), and so forth have been proposed. These methods may have an advantage of readily ensuring processibility, however, have a disadvantage that good encapsulation may be implemented with a single high molecular thin film due to high moisture retention and oxygen permeability of the high molecular thin film.